The present invention relates generally to vehicle emissions sensing systems. More particularly, the present invention relates to a method and system for determining, based on emissions data, the type of fuel that is used to power a vehicle.
To determine whether a vehicle is compliant with emissions standards, a knowledge of the fuel type is required, as different fuel types will exhibit different mixes of hydrocarbon species in exhaust. For example, a mix of hydrocarbons emissions that may comply with applicable emissions standards for diesel fuel may not comply with emissions standards that are applicable to another fuel such as gasoline. Thus, if the type of fuel that is used by the vehicle is not known, false readings of compliance or noncompliance with emission standards may result. In addition, as alternative fuels are developed, additional methods of determining fuel type become important to determine compliance with fuel type restrictions, manufacturer""s specifications, and emission regulations.
Unfortunately, current vehicle emissions measurement systems are not capable of automatically and reliably determining the type of fuel that is used to power the engine of a vehicle. This problem exists in both closed path and open path emissions measurement systems. In a closed path system, in which the emissions sensor is directly connected to the exhaust of the vehicle, attempts to overcome this problem have been limited to asking the vehicle""s owner what type of fuel has been placed into the vehicle""s fuel tank, as well as directly siphoning fuel and performing tests on such fuel. However, asking the vehicle""s owner is often an unreliable method of determining fuel type, and chemical analysis of fuel contained in the fuel tank is expensive and time-consuming. For open path vehicular emissions measurement systems, in which emissions data are collected by a means other than a direct connection to the tailpipe, such as a remote sensor that analyzes the components of emissions, the problem exists to a greater degree, as open path vehicular emissions systems are desirable in areas along roadways where, because the vehicle is moving, the vehicle""s owner cannot be asked fuel type, and fuel samples cannot be taken.
Also with an open path vehicular emissions testing system, the fuel type of a tested vehicle is obtained by matching the vehicle""s license plate against registration records that include fuel type information. This information can be incorrect because of benign misinformation in the registration database, or intentional, if a vehicle owner converts the vehicle to a different fuel type without informing the keepers of the registration database. For example, a vehicle registered to be diesel-powered is most likely to be exempted from periodic emissions inspections. However if the vehicle is converted to being gasoline powered without the knowledge of the keepers of the registration database, the vehicle should become subject to periodic inspection. This is a circumvention of vehicular emissions laws.
Accordingly, it is desirable to provide an improved method and system for automatically determining the type of fuel used to power a vehicle based on data corresponding to the emissions of the vehicle. It is also desirable that the method and system be capable of application in both closed path and open path vehicle emissions measurement systems.
It is therefore a feature and advantage of the present invention to provide a method of automatically determining the type of fuel used to power a vehicle based on emissions data.
The above and other features and advantages are achieved through the use of a novel fuel type determination method and system as herein disclosed. In accordance with one embodiment of the present invention, a method of determining the type of fuel used by a vehicle includes the steps of receiving first data and second collected by an emissions sensor. The first data corresponds to at least two measured hydrocarbon concentrations in a vehicle exhaust stream; while the second data corresponds to measured nitrogen-oxygen compound concentrations in the vehicle exhaust stream. The method also includes the steps of identifying at least one hydrocarbon threshold level corresponding to a first fuel type, comparing the first data to at least one of the hydrocarbon threshold levels; and determining whether the measured hydrocarbon concentrations correspond to at least one of the hydrocarbon threshold levels. In addition, the method includes identifying at least one nitrogen-oxygen compound threshold level corresponding to the first fuel type, comparing the second data to at least one of the nitrogen-oxygen compound threshold levels, and determining whether the measured nitrogen-oxygen compound concentrations correspond to at least one of the nitrogen-oxygen compound threshold levels.
In accordance with this embodiment, if the first determining step determines that the measured hydrocarbon concentrations do not correspond to at least one of the hydrocarbon threshold levels, the method may comprise the additional steps of identifying at least one hydrocarbon threshold level corresponding to a second fuel type, comparing the data to at least one of the hydrocarbon threshold levels corresponding to the second fuel type, and determining whether the measured hydrocarbon concentrations correspond to at least one of the hydrocarbon threshold levels corresponding to the second fuel type. In addition, if the second determining step determines that the measured nitrogen-oxygen compound concentrations do not correspond to at least one of the nitrogen-oxygen compound threshold levels, the method may include the additional steps of: identifying at least one nitrogen-oxygen compound threshold level corresponding to a second fuel type, comparing the second data to at least one of the nitrogen-oxygen compound threshold levels corresponding to the second fuel type, and determining whether the measured nitrogen-oxygen compound concentrations correspond to at least one of the nitrogen-oxygen compound threshold levels corresponding to the second fuel type.
The threshold levels are preferably stored in a computer memory or carrier, and may optionally comprise a percentage or a range. When the threshold level comprises a percentage, correspondence preferably comprises a determination that the measured concentration is equal to or greater than the percentage. Where the threshold level comprises a range, correspondence preferably comprises a determination that the measured concentration falls within the range.
In accordance with an alternate embodiment of the present invention, a method of determining the type of fuel used by a vehicle includes the step of receiving data collected by an emissions sensor, wherein the data corresponds to a plurality of measured hydrocarbon and nitrogen-oxygen compound concentrations in a vehicle exhaust stream. The method also includes calculating, for each of a plurality of possible fuel types, an associated probability. The associated probability corresponds to the plurality of measured hydrocarbon and nitrogen-oxygen compound concentrations. The method also includes selecting a highest probability from the associated probabilities and reporting the possible fuel type having the associated probability that is the highest probability.
In accordance with either of the above-described embodiments, the fuel types preferably include diesel fuel, gasoline, compressed natural gas, methanol, reformulated gasoline, and/or liquified petroleum gas. Where a fuel type comprises diesel fuel, the methods preferably include comparing measured concentrations to threshold levels of methane and carbonyl species comparing measured concentrations to threshold concentrations of nitrogen dioxide. Where a fuel type comprises compressed natural gas, and the methods preferably include summing measured concentrations of alkanes, alkenes, alkynes, and methane and comparing the measured concentration of methane to the total sum. Where a fuel type comprises liquified petroleum gas, the method preferably includes (i) determining a total hydrocarbon measurement comprising a sum of measured concentrations of alkanes, alkenes, alkynes, and methane; (ii) determining a percentage of propane relative to the total hydrocarbon measurement; and (iii) determining whether the percentage of propane exceeds a predetermined propane threshold. Where a fuel type comprises methanol or reformulated gas, the method preferably includes: (i) identifying relative concentrations of carbon, hydrogen, and oxygen that are typical for a reference fuel; (ii) determining whether the relative concentration of oxygen is greater than zero; (iii) selecting, from the measured hydrocarbon concentrations, a first concentration corresponding to alkanes and a second concentration corresponding to methanol and reformulated gasoline species; (iv) scaling the first concentration and the second concentration to adjust for at least one interference; and (iv) comparing the first concentration and the second concentration.
Another embodiment of the present invention provides a system for the implementation of one or more of the above-described methods. The system includes an emissions sensor or other means capable of measuring hydrocarbon and nitrogen-oxygen compound concentrations in a vehicle exhaust stream. The system also includes a processor in communication with the emissions sensor, and a memory or other carrier in communication with the processor. The carrier contains computer program instructions that instruct the processor to implement one or more of the above-described methods.
There have thus been outlined the more important features of the invention in order that the detailed description thereof that follows may be better understood, and in order that the present contribution to the art may be better appreciated. There are, of course, additional features of the invention that will be described below and which will form at least part of the subject matter of the claims appended hereto.
In this respect, before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein, as well as the abstract included below, are for the purpose of description and should not be regarded as limiting in any way.
As such, those skilled in the art will appreciate that the concept and objectives, upon which this disclosure is based, may be readily utilized as a basis for the design of other structures, methods and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention.